Elastic thread and elastic fabric



Feb 11, I941. A. xsAAc ELASTIC THREAD AND ELASTIC FABRIC Filed Nov -20,1937' Patented Feb. ll, 1941 UETE STTES PATENT OFFICE Augustin llsaac,Lyon, France, assignor to Dognin, Societe Anonyme, Villeurbanne, Rhone,France,

a French company Application November 20, 1937, Serial No. 175,723

- In France November 26, 1936 4 Claims.

The present invention relates chiefly to elastic fabrics and moreespecially those which are made of at least two sets of threads. As itwill result from the following description, the word fabric should betaken in its broadest meaning, including in a general manner anymanufactured product obtained by a combination, according to a givensystem, of thread-like elements which cross one another. The inventionis more especially, although not exclusively, applicable to open workfabrics generally made with an elastic war-p of rubber threads suitablycovered (these threads being round, square, etc.) and to close meshfabrics the elastic warp of which is' made, on the contrary, of barerubber threads, suitably associated with and maintained by inextensiblefibers, either in the direction of the warp or in the direction of theweft, or again in both directions. Besides, in

the following specification, the words warp andweft can be interchanged,the reference to an elastic warp and a non-elastic weft being mademerely in order to simplify the language in the description.

For the same reason, the word rubber will be used in a generic manner,designating not only rubber proper but any matter having equivalentqualities and in particular having a good elas- ,ticity corresponding tothat of rubber proper.

In open work elastic fabrics, and especially when the threads of the twogroups (warp and weft) have sections of the same order of magnitude,each weft thread is liable to slide at the point where it crosses eachWarp thread, with respect thereto (and inversely) when the fabric issubjected to stresses of a nature to cause such displacements of thethreads. As a matterof fact, in opposition to what takes place for theelements constituting close mesh fabrics, the threads of these open workfabrics are not, as a rule, maintained at the cross points by theadjacent threads of the same kind, and in this case only mutual frictionbetween threads of different natures tends to prevent relative slidingdisplacements. In many circumstances, this friction has provedto beinsuflieient. it is therefore interesting to be able to improve theinterconnection of the threads at the crossing points without beingcompelled to modify the structure of the fabric.

This improvement is still more necessary in the case of extensiblefabrics of the open work kind than in the case of inextensible open workfabrics because the successive elongations and reductions of lengthundergone by the rubber warp threads.

produce corresponding variations of section of the er as to prevent asfar as possible, a relative threads which, in the case of reduction ofsection, facilitate the relative sliding of the threads.

In a general manner, the object of the present invention is to reduce asmuch as possible the two drawbacks above mentioned.

More specifically an object of the present invention is to providethreads of a particular kind the use of which permits of avoiding thesedrawbacks.

Another object of the invention is to provide elastic fabrics made withsuch threads and consequently avoiding the drawbacks above pointed out.

Still another object of the invention is to pro-- vide a methodofmanufacturing the fabrics in question.

The elastic threads according to the present invention are essentiallycharacterized by the fact that they have, superficially, projectionsalternating, in the direction of the length, with hollows, theseunequalities being of such an amplitude and at such intervals from oneanother that they are capable of preventing relative sliding movement ofcross-threads contacting the improved elastic threads.

The elastic fabrics according to the present invention are alsocharacterized by'the fact that, among the groups of threads whichconstitute them, at least one of these groups includes, eitherexclusively or partly, threads of an elastic nature provided withunequalities as above mentioned, these threads being for instance warpthreads. The amplitude of the unequalities and the interval from one tothe other, in the longitudinal direction, are generally chosen inaccordance with the size of the threads of the other group and theinterval between these last mentioned threads, in such manner that thelatter are supported by the threads of the first mentioned group in suchman sliding. However, in certain cases, this choice of a particularrelation between the amplitude and the interval of the unequalities onthe one hand and the size and interval of the threads of the secondgroup on the other hand is not absolutely necessary; in some fabricswhere weft threads are looped around or make a turn about the warpthreads, said weft threads are nearly at right angles to the warpthreads, and they always find on a portion of their loops around suchwarp 5 threads a recessed portion into which they penetrate, provided,of course, that the amplitudeand interval of the unequalities, withouthaving to be too great, are however sufllcient..

In order to obtain elastic threads having the necessary superficialunequalities, I may, first, produce these unequalities by suitablymodifying the covering of the threads, without imposing any particularcondition to the longitudinal section of the rubber core of saidthreads. Thus, instead of trying to obtain, as it was the case up tonow, in all covered threads,'a surface as smooth as possible despite thevarious technical requirements which sometimes make this difficult toobtain, I can obtain very simply alternating projections and hollows ofsufficient size by placing, on the surface of the elastic core, a helixof a thread sufllciently big, in point of fact bigger than the threadsused up to the present time (which are strictly suflicient formaintaining the core in an already tensioned state at rest); Thediameter and the rigidity of the thread of this helix are chosen in suchmanner that the helical thread forms on the rubber core a projectionwhich is sufficient even if the helical thread penetrates slightly intothe surface of said rubber core. For practical purposes, I may cover thecore with a first ordinary covering the convolutions of which are inadjoining or nearly adjoining relation to each other, and I positionthereover a thick thread in the form of an open spiral and (or) I coverthe core having already received the helix of thick thread with anordinary external covering. However, I prefer,- ably make use of thishelix, which is of course very strong, in such manner that itconstitutes, at least partly, the covering of the rubber core, or one ofthe coverings. When use is made of two coverings, an inner covering andan outer covering, and

when they are treated differently and are such that it is chiefly one ofthem which limits the elongation of the elastic thread, it is this lastmentioned covering whichis preferably chosen for incorporating the helixtherein. In this manner, I make sure that in the state of tension, thiselongated helix will make the minimum angle with the axis of the core oreven will be so deeply imbedded into the surface of the core as toproject by less amount with respect to the general surface of the core,as it is well known in the art.

If the helixis to constitute the external part of the finished elasticthread, it can, in some cases in which it is not desired to obtain avery dense covering, constitute the whole of the external covering, oron the contrary, it may constitute it in combination with other threadswhich are thinner, for instance of ordinary size, and-the convolutionsof which are inserted between the convolutions of the big helix. In thiscase, it is the difference between the diameters of these two externalcovering threads which determines the importance of the projections. Theefficiency of the big thread helix is of course greater if this helix islocated above an external thread covering having substantially adjoiningconvolutions and if its pitch is. greater than that of said threadcovering. However, this necessitates the fitting of a third spindle onthe thread covering machine.

If, on the contrary, the helix is in contact with the rubber, under anexternal thread covering, it can also constitute or not, by itself, theinner thread covering, but it is necessary to take into account its moreor less accentuated sinking into the rubber core. But, on the otherhand, the external thread covering is then made, in the usual manner,with fine thread, so that the reliefof the helix is not materiallyattenuated and on .the contrary the helix is still better anchored,without any risk of displacement along the rubber surface.

Instead of forming projections with the helix produced by a single bigthread, I may, on the contrary, form this helix with a plurality ofparallel fine threads, placed simultaneously on the core by the threadcovering machine, in such manner that they accumulate locally on thecore (which is provided or not with a first uniform thread covering) insuch manner as to form a spiral-shaped projection the spires of whichare not in adjoining relation to one another.

Besides, in both cases, I may provide, instead of a single spiral,several spirals each constituted from a single thread or from a sheaf ofthreads, these spirals being analogous to the threads of a multi-threadscrew.

The material constituting-the big thread of the helix or of theequivalent sheaf of threads is not necessarily an unextensible material.Advantageously, in some cases, it can also be elastic, the thread or thesheaf of threads being either covered or not. For instance it ispossible toobtain a better adhesion in this way. Furthermore, the normalstretching capability of the whole is not limited by the helix,especially when the latter is obtained by means of a third spindle, byplacing this helix above the external thread covering and with a largerpitch.

The direction of winding of the helix on the warp thread may be chosenin accordance with the structure of the fabric to be obtained, in suchmanner as to correspond to the direction of the greater number of loopsproduced by the weft on the warp, when such loops exist. If, on thewhole, the fabric includes as many right hand loops as left hand loops,it is generally unnecessary to bother with the direction of winding ofthe helix, except when the loops of inverse directions are located ondifferent warp threads. If, on the contrary, it is on each thread thatthe weft threads are successively wound by forming loops in inversedirections, generally those in a certain direction will produce,according to the structure of the fabric, the best connection with thewarp thread, by opposition with the other direction, and this will besufficient in most cases for avoiding slipping.

The slight increase of the total section of the elastic thread willgenerally be without any disadvantageous consequence because theelimination of slipping permits, for a given section, of utilizingstronger threads which are stretched to a higher'degree and bettercovered, the latter being, generally, more fully covered and therefore vthe less capable of being used as a consequence of the fact that theirsurface is nearly continuous, when the covering is made in the usualmanner, for instance with ordinary cotton threads.

Especially for the manufacture of open work fabrics with covered elasticthreads, it even suffices, in some cases, instead of making in advancean elastic thread having projections alternating with hollows in thelongitudinal direction, of making the external covering of this threadin such manner that these projections may be produced, so to speakautomatically, at the end of the manufacture of the fabric when thelatter, removed from the frame, undergoes contraction or even only atthe time of the use, when the causes above pointed out have a tendencyto cause the weft thread to slip and, consequently, to compress the warpthread covering between its loops.

By way of example, I may make use, for constituting this externalcovering, of artificial silks oranalogous threads (and even in somecases of silk, either raw or not) the fibers of which, of very greatlength, are assembled with a recost of a certain lack of stability ofthe covered thread, due to the defective resistance of this material towater and moisture, in particular to perspiration. 0n the contrary, Imay make use of acetate silk or any other analogous matter resistingmoisture and which, in spite of its utilization in the untwistedstate,is however capable of satisfactorily hooping the thread and giving itthe necessary stability in service.

I thus obtain, owing to the retraction of the warp threads of thefabric, which contracts for the first time when leaving the frame, atrue imbedding of the weft threads in the external covering of the warpthreads, owing to the relative freedom of the elementary threadsslipping on one another due to their smooth surface. In order to obtainthis imbedding in a still better manner, I may take the maximumadvantage of the period of distension of the covered threads, in whichthe covering is floating, as if it, were released from the core. Insteadof unwinding without precaution'from the roll of fabric the part thathas been recently made, I cause it to pass on a special rollerpermitting, through suitable means, for instance by means of jawsapplied on the edges, of tensioning to the maximum degree, inthedirection of the width, the fabric as it passes from one rollerto'the other, being distended in the longitudinal direction.

Once the fibers, temporarily malleable, have settled in position on thesurface of the warp threads, imprisoning the bobbin threads passingamong them and shaping tour thereof, they tend subsequently -to keepthis position and they resist the actions urging the bobbin threads inthe direction of the warp threads, by bearing upon one another and uponthe surface of the core with which they'are at least partly in contact.

Finally, it is possible to combine an inner covering, made either whollyor partly of a big helix, with an external covering of acetate silk.

Of course, the rubber that is utilised can, instead of a single thread,consist of a sheaf of elastic threads.

The invention is also applicable to openwork fabrics with multiple warpthreads, that is to say; in which each warp thread is constituted ofseveral separate elementary threads covered individually. It suffices tochoose accordingly the pitch of the helixon each individual thread.Besides the threads may be only provided therewith for some of them.

The invention further applies to dense and close-meshed fabrics madewith elastic warp threads which may be covered or not. In fabrics ofthis kind, if such a thread breaks, the alternations of tension and lackof tension cause the two elements of which the thread is made to retractgradually, producing generally a characteristic sinuous line, and thuscreating, in addition to a defect which is disagreeable to see, a lineof reduced resistance.

In this case, it is the rubber thread itself themselves to theconknitted, with which, according to the present invention, is providedwith superficial unequalities. The latter may be created by producingone or more spirals in relief or in hollow but the projections may begiven the shape of rings alternating with grooves. These variations ofsection may be produced at the end of the manufacture of the thread bythe provision of notches or the like, either annular or not, or even, inthe case of threads of square section, by periodically notching theedges.

Said variations of section may, on the contrary, be produced during themanufacture; for instance in the case of a thread produced by drawing orin an analogous manner, by a quick and periodical change of the heightof liquid above the holes through which the drawing takes place, or byquick modifications of its pressure, for instance by the application ofvibrations. They can also be produced by providing projections in thegrooves of a drum which, in the known man;

' ner, turns in a bath, of liquid rubber, so as to take highly resistantthread, the spires of which do not adjoin one another, in such manner.as to produce in the gum correlative recesses and projectionssufiiciently intensive for remaining when the thread undergoes amoderate elongation. I may consequently make use of threads of this'kind when their elongation is limited inside the fabric under normalconditions of use of the fabric, or again is limited by auxiliary warpthreads, inextensible and parallel to the direction of said elongation.Besides, a double covering may be constituted insuch manner that itsnon-adjoining spires produce in the uncovered portions a diametersubstantially greater than that of the covered portions, including thecovering, even when the gum undergoes a moderate elongation.

In a more general manner, the invention can be applied to all kinds offabrics, close or loose or without meshes, making use, either as warp oras weft of elastic rubber threads which are either thread covered ornot.

The invention also applies to the inextensibie fabrics of the open meshor net type, in particular to nets or laces and in this case it permitsof avoiding deformations of the nets caused by the slipping of thethreads of one group on the threads of the other group. It may only benecessary in this application to arrange that the'projections barethreads, the projections must be given a suitable angle, facilitatingweaving as much as possible, when the thread is fully stretched.

utilized on the inextensible threads of one of the Preferred embodimentsof the present invention will be hereinafter described, with referenceto the accompanying drawing, given merely by way of example, and inwhich:

Figs. 1 to 3 diagrammatically show three specific forms of coveredrubber threads made in accordance with my invention.

Figs. 4 and show two specific forms of naked rubber threads also inaccordance with my invention.

Fig. 6 shows another form of rubber thread with an open-spiral coverthread wound thereabout.

Fig. 1 shows, on an enlarged scale, a portion of an elastic threadincluding a core I surrounded with a relatively big thread 2 which isarranged to form a helix with non-adjoining spires, the whole beingembedded in the external covering 3 of fine thread, wound in theopposite direction.

In Fig. 2, the core I is' provided with a first covering 4, which issurrounded by a big thread 2 having non-adjoining spires,and'simultaneously by a covering 5 of fine thread, disposed between thespires of the big thread 2.

Fig. 3 shows a thread provided with the two usual coverings l and I2,the latter being covered by a big helix 2 of a difierent pitch.

Fig; 4 shows a thread 6 of bare rubber provided with peripheral groovesI.

Fig. 5 shows the same thread in the elongated state, the grooves nowmaking but a small angle with the thread itself, in such manner as tointerfere as little as possible with the weaving.

Fig. 6 shows a rubber thread 8 of square section, which thread issurrounded by the non-adjoining spires of an inextensible thread 9fitting in notches ill or merely applied upon the unmodified threadunder a tension such that a pronounced swelling takes place at llbetween two consecutive spires isandl the two grooves produced by them,respec- Figure 7 illustrates another embodiment of the invention inwhich the resilient core I is first wound with a layer of fine coverthreads l3. and then a large cover thread It in spaced helical form iswound about the first layer and preferably in the opposite direction. a

In a general manner: while I-have. in the above description, disclosedwhat I deem to be practical and efiicient embodiments of the presentinvention, it should be well understood that I do not wish to be limitedthereto as there might be changes made in the arrangement, disposition,and form of the parts without departing from the principle of thepresent invention as comprehended within the scope of the accompanyingclaims.

What I claim is:

1. An elastic thread which comprises a core of elastic material: aninnermost cover on the core; a coarse cover thread spirally wound aboutthe innermost cover to form an outstanding openspiral rib on the same;and a filling cover of fi'ne thread positioned on the innermost cover tospan, in sunken relief, the interval between proximate convolutions ofthe outstanding rib.

2. An elastic thread which comprises a. core of elastic material; aninner cover on the core, the

outer surface of which is formed by convolutions of fine thread wound inone direction: and a coarse cover thread exposed throughout its length,spirally wound over the outer surface of the inner cover, in a directionopposite to the aforesaid direction to form an outstanding open spiralrib on the same.

3. An elastic thread which comprises a core 'of elastic material; atleast one substantially even cover on the core, consisting of' spirallywound fine cover threads; and a big thread wound in the form of acontinuous open spiral helix over the even cover, positioned outwardlywith respect to any and all the fine cover threads in the even coverwhich it contacts, so as to be throughout in exposed operative position.

4. In an elastic thread having a plurality oi covers arranged to providelocal projections on the external surface of said thread, thecombination of a core of elastic material with a cover of spirally woundfine threads, and a thick even rib which is disposed on one side withrespect to the cover of spirally wound fine threads, follows an openspiral line and produces an even, open spiral projection on the elasticthread surface, throughout the length of said thread.

AUGUSIIN ISAAC.

